/*
 Copyright  2002-2004 MySQL AB, 2008 Sun Microsystems
 All rights reserved. Use is subject to license terms.

  The MySQL Connector/J is licensed under the terms of the GPL,
  like most MySQL Connectors. There are special exceptions to the
  terms and conditions of the GPL as it is applied to this software,
  see the FLOSS License Exception available on mysql.com.

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation; version 2 of the
  License.

  This program is distributed in the hope that it will be useful,  
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
  02110-1301 USA



 */
package com.mysql.jdbc;

/**
 * EscapeTokenizer breaks up an SQL statement into SQL and escape code parts.
 * 
 * @author Mark Matthews
 */
public class EscapeTokenizer {
	// ~ Instance fields
	// --------------------------------------------------------

	private int bracesLevel = 0;

	private boolean emittingEscapeCode = false;

	private boolean inComment = false;

	private boolean inQuotes = false;

	private char lastChar = 0;

	private char lastLastChar = 0;

	private int pos = 0;

	private char quoteChar = 0;

	private boolean sawVariableUse = false;

	private String source = null;

	private int sourceLength = 0;

	// ~ Constructors
	// -----------------------------------------------------------

	/**
	 * Creates a new EscapeTokenizer object.
	 * 
	 * @param s
	 *            the string to tokenize
	 */
	public EscapeTokenizer(String s) {
		this.source = s;
		this.sourceLength = s.length();
		this.pos = 0;
	}

	// ~ Methods
	// ----------------------------------------------------------------

	/**
	 * Does this tokenizer have more tokens available?
	 * 
	 * @return if this tokenizer has more tokens available
	 */
	public synchronized boolean hasMoreTokens() {
		return (this.pos < this.sourceLength);
	}

	/**
	 * Returns the next token
	 * 
	 * @return the next token.
	 */
	public synchronized String nextToken() {
		StringBuffer tokenBuf = new StringBuffer();

		if (this.emittingEscapeCode) {
			tokenBuf.append("{"); //$NON-NLS-1$
			this.emittingEscapeCode = false;
		}

		for (; this.pos < this.sourceLength; this.pos++) {
			char c = this.source.charAt(this.pos);

			// Detect variable usage

			if (!this.inQuotes && c == '@') {
				this.sawVariableUse = true;
			}

			if ((c == '\'' || c == '"') && !inComment) {
				if (this.inQuotes && c == quoteChar) {
					if (this.pos + 1 < this.sourceLength) {
						if (this.source.charAt(this.pos + 1) == quoteChar) {
							// Doubled-up quote escape, if the first quote isn't already escaped
							if (this.lastChar != '\\') {
								tokenBuf.append(quoteChar);
								tokenBuf.append(quoteChar);
								this.pos++;
								continue;
							}
						}
					}
				}
				if (this.lastChar != '\\') {
					if (this.inQuotes) {
						if (this.quoteChar == c) {
							this.inQuotes = false;
						}
					} else {
						this.inQuotes = true;
						this.quoteChar = c;
					}
				} else if (this.lastLastChar == '\\') {
					if (this.inQuotes) {
						if (this.quoteChar == c) {
							this.inQuotes = false;
						}
					} else {
						this.inQuotes = true;
						this.quoteChar = c;
					}
				}

				tokenBuf.append(c);
			} else if (c == '-') {
				if ((this.lastChar == '-')
						&& ((this.lastLastChar != '\\') && !this.inQuotes)) {
					this.inComment = true;
				}

				tokenBuf.append(c);
			} else if ((c == '\n') || (c == '\r')) {
				this.inComment = false;

				tokenBuf.append(c);
			} else if (c == '{') {
				if (this.inQuotes || this.inComment) {
					tokenBuf.append(c);
				} else {
					this.bracesLevel++;

					if (this.bracesLevel == 1) {
						this.pos++;
						this.emittingEscapeCode = true;

						return tokenBuf.toString();
					}

					tokenBuf.append(c);
				}
			} else if (c == '}') {
				tokenBuf.append(c);

				if (!this.inQuotes && !this.inComment) {
					this.lastChar = c;

					this.bracesLevel--;

					if (this.bracesLevel == 0) {
						this.pos++;

						return tokenBuf.toString();
					}
				}
			} else {
				tokenBuf.append(c);
			}

			this.lastLastChar = this.lastChar;
			this.lastChar = c;
		}

		return tokenBuf.toString();
	}

	boolean sawVariableUse() {
		return this.sawVariableUse;
	}
}
